My name is Erin McGonigal and I'm an assistant professor at the Medical College of Wisconsin. I will be talking about common anatomical patterns of spasticity. I do not have any relevant financial relationships to disclose. The learning objectives of this module include being able to describe common upper limb patterns of spasticity, being able to describe common lower limb patterns of spasticity, and identifying the common muscles involved in each of these postures. While presentations of spasticity in the upper limb can be variable, the most common pattern involves a combination of adduction and internal rotation of the shoulder, flexion of the elbow, pronation of the forearm, flexion of the wrist and fingers, and flexion as well as adduction of the thumb. Adduction and internal rotation of the shoulder result from involvement of the pectoralis major, pectoralis minor, and latissimus dorsi. Abnormal tone in these muscles can also contribute to hemiplegic shoulder pain as well as place patients at a higher risk of developing adhesive capsulitis or a frozen shoulder. The major muscles contributing to elbow flexion tone are the brachialis and the biceps brachii proximally and the brachioradialis distally. While the biceps brachii is an on-label muscle for botulinum toxin injections, injections to this muscle should be carefully considered as it is also a strong supinator of the forearm in patients who tend to be overpronated. Pronation of the forearm is contributed to by the pronator teres proximally and pronator quadratus distally. The pronator teres is more likely to be targeted with botulinum toxin injections. The major muscles contributing to wrist flexor spasticity are the flexor carpi radialis, flexor carpi ulnaris, flexor digitorum superficialis, and flexor digitorum profundus, all of which are targeted for injection in the ventral forearm. It is important to note that while the main function of the long finger flexors is finger flexion as the name implies, they cross the wrist joint and thus contribute to wrist flexion as well. The FDS, FDP, and lumbricals all contribute to finger flexion postures. The lumbricals act at the MCPs, the flexor digitorum superficialis at the MCPs and PIPs, and the flexor digitorum profundus at the MCPs, PIPs, and DIPs. These connect individually or in combination depending on the patient. Even in a patient without active use of the hand, opening up the fingers is important in maintaining hand hygiene and preventing skin breakdown in the palm of the hand. The combination of thumb adduction, flexion, and opposition produces what is known as the thumb and fist position. The main muscles involved are the flexor pollicis longus and brevis for thumb flexion and adductor pollicis and opponent's pollicis for thumb adduction and opposition. The flexor synergy pattern most commonly observed in the lower limb consists of a combination of adduction, flexion and internal rotation of the hip, flexion of the knee, ankle flexion and inversion, and toe flexion. The great toe is often flexed but can be held in extension as well. The most common muscles contributing to spasticity at the hip include those involved in hip adduction, flexion, and internal rotation. The adductor longus, adductor brevis, and adductor magnus, as the names imply, all cause hip adduction. Spasticity in these muscles can cause a scissoring gait in an ambulatory patient or interfere with positioning in a wheelchair. The gracilis, while a smaller muscle, contributes to adduction, flexion, and internal rotation. The rectus femoris is the only of the quadriceps to cross the hip joint and therefore contributes to hip flexion. The iliopsoas, while slightly more challenging to localize for injections, is also an important hip flexor. The hamstrings are usually the strongest contributor to knee flexion spasticity. The gracilis, sartorius, and gastrocnemius can all contribute as well. Spasticity in these muscles can limit knee extension in the swing phase of gait in an ambulatory patient, and when more severe it can interfere with wheelchair seating and positioning. Proper wheelchair seating is very important to prevent the development of pressure sores. The typical ankle position seen in spasticity is both flexed and inverted, though the two can appear in isolation. The gastrocnemius and soleus combine in the Achilles tendon, which contributes almost entirely to plantar flexion. The tibialis posterior contributes to both ankle flexion and inversion, and is one of the strongest ankle inverters. The tibialis anterior contributes to ankle inversion as well, but is rarely targeted for botulinum toxin injection due to the risk of dorsiflexion weakness. The flexor hallucis longus and flexor digitorum longus cause flexion of the great toe and the remainder of the toes respectively, and also contribute to ankle flexion and inversion because they cross the ankle joint. Toe flexion spasticity is mediated by both long toe flexors, the flexor digitorum longus and flexor hallucis longus, as well as the foot intrinsics, flexor digitorum brevis and flexor hallucis brevis. The long toe flexors are generally preferred for botulinum toxin injections as they are approached in the leg rather than the foot itself, which is less uncomfortable. Which of the following muscles does not contribute to wrist flexion? A. brachioradialis, B. flexor carpi radialis, C. flexor carpi ulnaris, D. flexor digitorum profundus. The correct answer is A. The brachioradialis does not cross the wrist joint and therefore does not contribute to wrist flexion. The remaining three choices all cross the wrist joint. In summary, spasticity most often presents in predictable patterns in the upper and lower extremities. Recognizing these patterns and knowing the muscles involved is integral to successful treatment of vocal spasticity.

spasticity

upper limb

lower limb

anatomical patterns

treatment